Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is none, oncePerWeek, severalPerWeek or daily.
Build a proper factor for the responses below and store it in a variable w.
Print the factor.
Write the code to count the numbers of occurrences of each level and print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek
[8] <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 x 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the results.
Next, understand why an error is generated and use replace argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor w from it.
Finally, count the numbers of occurrences of each level in w.
Ensure, that levels are in order provided in the variable lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "severalPerWeek" "none" "daily"
sample( lvs, 3 )
[1] "daily" "oncePerWeek" "none"
sample( lvs, 3 )
[1] "oncePerWeek" "severalPerWeek" "daily"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] daily severalPerWeek daily oncePerWeek none severalPerWeek oncePerWeek
[8] daily severalPerWeek oncePerWeek oncePerWeek severalPerWeek daily none
[15] daily daily severalPerWeek daily none none oncePerWeek
[22] none daily oncePerWeek none none daily oncePerWeek
[29] none oncePerWeek severalPerWeek severalPerWeek oncePerWeek none severalPerWeek
[36] none severalPerWeek none none oncePerWeek severalPerWeek severalPerWeek
[43] daily oncePerWeek severalPerWeek oncePerWeek severalPerWeek daily severalPerWeek
[50] none severalPerWeek daily daily daily severalPerWeek oncePerWeek
[57] daily none severalPerWeek severalPerWeek daily severalPerWeek daily
[64] none daily none severalPerWeek daily none oncePerWeek
[71] severalPerWeek severalPerWeek none none oncePerWeek none none
[78] none severalPerWeek oncePerWeek daily severalPerWeek oncePerWeek daily
[85] none daily daily oncePerWeek none severalPerWeek daily
[92] daily none daily daily none none oncePerWeek
[99] daily severalPerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 x 2
f n
<fct> <int>
1 none 27
2 oncePerWeek 19
3 severalPerWeek 26
4 daily 28
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its levels.
The factor w from the previous exercise will be then shown in this order: none, oncePerWeek, severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed: daily, severalPerWeek, oncePerWeek, none.
Apply to w one of the fct_ functions from the tidyverse library to produce a factor w2 with the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 x 2
f n
<fct> <int>
1 daily 28
2 severalPerWeek 26
3 oncePerWeek 19
4 none 27